Recently especially in United States, the needs is rapidly increasing for the plastic base material using a polycarbonate of transparent and having excellent impact resistance, for the use of the sunglasses with a anti glare property. Further, in regards with such plastic sunglass, the photochromic sunglass made of plastic is rapidly becoming popular which can control the anti glare property by changing a transparency depending on the surrounding brightness by combining with a photochromic pigments. Such sunglasses can be produced by the following method.
For example, as a method for producing photochromic sunglasses made from plastic having a high impact resistance, a known method is to produce said sunglasses by dispersing a photochromic compound into a polyurethane-urea resin (refer to Patent Literature 1 to 4). These documents describe a method in which a composition including a polyurethane-urea resin and a photochromic compound is used as is to make the sunglasses (body casting method), and a method in which said composition is coated onto a base material formed from other materials to make the sunglasses (coating method). According to these methods, since the photochromic compound is dispersed in the polyurethane-urea resin, sunglasses having a high impact resistance and excellent photochromic characteristics can be produced.
However, since these methods are methods for directly producing sunglasses, these methods have not been widely used for other applications. For example, since in the body casting method the composition is poured into a lens mold, it has not been possible to use this method for other shapes. Further, for the coating method also, since a coating layer is formed by coating the composition on a lens base material, it has not been possible to use this method for other shapes.
In order to improve on the above points, proposals such as the following have been made. For example, a lot of investigation has gone into methods using a polyurethane adhesive layer including a photochromic compound to impart photochromic characteristics to variously shaped base materials. Specific examples include methods of using a “multilayer sheet binding the polycarbonate sheet with a polyurethane resin adhesive layer containing a photochromic pigment” (refer to Patent Literature 5 and 6). Using such a multilayer sheet enables photochromic characteristics to be imparted to various base materials regardless of their shape. Specific examples of a method for producing sunglasses that utilize this multilayer sheet include a method in which said multilayer sheet is installed into a metal mold and a polycarbonate resin is injection molded therein.
However, in these conventional methods, the adhesion of the polycarbonate sheet in the above-described multilayer sheet and the heat resistance of the adhesive layer itself are insufficient. Consequently, when an optical article is produced by installing the multilayer sheet into a metal mold and then injection molding a polycarbonate resin into said metal mold, there were problems such as peeling of the obtained optical article and optical strain or so.
Further, based on investigations by the present inventors, in the method that uses the above-described multilayer sheet, it was learned that when the polyurethane-urea resin described in Patent Literature 1 to 4 was used for the polyurethane resin adhesive layer, for example, the adhesion to the polycarbonate are not sufficient.
In addition, depending on how they are used, photochromic sunglasses may need to have “perspiration resistance” (there is a need for sunglasses that do not undergo a state change even when they come into contact with human perspiration). However, for sunglasses that use a conventional multilayer sheet, peeling of the polycarbonate sheet and the like is observed, so that such sunglasses do not sufficiently meet this need.